Polyalkylene ether glycol copolymers

ABSTRACT

Polyalkylene ether glycol copolymers having a number-average molecular weight of from 200 to 10,000 and having hydroxyl groups at both ends of the molecule are disclosed. The copolymers are comprised of recurring structural units of the following formulae (I) and (II) in a molar ratio range (I/II) of from 1/99 to 99/1: ##STR1##

This application is a continuation of U.S. Ser. No. 511,380, filed July6, 1983, now abandoned.

The present invention relates to new polyalkylene ether glycolcopolymers.

More particularly, the present invention relates to new polyalkyleneether glycol copolymers containing 2-methylpropylene ether groups andtetramethylene ether groups as recurring structural units of thecopolymers.

Known polyalkylene ether glycols include polyethylene glycol, poly-1,2-and 1,3-propylene ether glycol, polytetramethylene ether glycol,polyhexamethylene ether glycol and copolymers of them. They have beenused widely as lubricants or as starting materials for preparinglubricants used in the molding of rubbers and in the treatment offibers, ceramics and metals. They have also been used as importantstarting materials for preparing cosmetics and medicines, as startingmaterials or additives for water-based paints, paper coatings,adhesives, cellophane, printing inks, abrasives and surfactants and asstarting materials for preparing resins, such as alkyd resins.

Thermoplastic elastomers having an intrinsic molecular structure whichexhibits elastic properties, unlike elastomers formed in the prior artby chemical crosslinking, such as rubber, have been developed and widelyused in practice. The thermoplastic elastomers have various advantages,for example, they can be processed easily, the processing time is short,scraps of them can be reutilized easily and wide ranges of mechanicalproperties ranging from rigid to soft properties can be obtained easily.These elastomers are expected to have great commercial possibilitiesbecause they fill gaps that exist between conventional thermoplasticresins, thermosetting resins and vulcanized rubbers. The thermoplasticelastomers now available on the market can be classified broadly intothe groups of poly(styrene-butadiene), polyesters, polyamides,polyurethanes and blends of ethylene/propylene copolymer rubber withpolypropylene. Except for the latter blend, they are typical blockcopolymers obtained by incorporating blocks of soft and hard segmentsinto a straightchain structure in the course of the polymerization. Ascompounds that are frequently used as the soft segments for elastomers,such as polyester, polyamide and polyurethane elastomers, there can bementioned polyalkylene ether glycols. The reason for this is thatbecause the polyalkylene ether glycols have hydroxyl groups at both endsthereof, they are highly reactive with carboxyl and isocyanate groupswhereby to form ester and urethane bonds, respectively. Further, sincethe polyalkylene ether glycols have ether bonds in their skeletons, theresulting polymers have a high elasticity and excellent properties, suchas low temperature properties and resistance to hydrolysis, salt waterand bacteria. The function of the polyalkylene ether glycol as the softsegment is closely related to the chemical structure and physicalproperties thereof. To exhibit the above-mentioned advantages, it isdesirable, from the viewpoint of reactivity, that the hydroxyl groups atboth ends of the alkylene ether glycol are primary hydroxyl groups and,from the viewpoints of elasticity and elastic recovery, that it has alow glass transition temperature and that it per se does notcrystallize, even when it has a high molecular weight. However,polyalkylene ether glycols having both the above-mentioned chemicalstructure and physical properties have not been known. For example,polyethylene glycol and polytetramethylene ether glycol, which are usedfrequently as soft segments, have a high reactivity because they haveprimary hydroxyl groups at both ends. However, if they have a molecularweight of higher than about 1500, they crystallize and become unable toexhibit a sufficient function as the soft segments of the thermoplasticelastomer. On the other hand, polypropylene ether glycols have anunfavorably poor reactivity because one of their terminal hydroxylgroups is a secondary hydroxyl group, although they are advantageous inthat they scarcely crystallize even when the molecular weights thereofare increased. There have been known polyalkylene ether glycols havingprimary hydroxyl groups at both ends which polymers are obtained bycopolymerizing propylene oxide with ethylene oxide and which polymersscarcely crystallize even when the molecular weights thereof areincreased. However, they cannot exhibit sufficient elasticity andelastic recovery effects required of the soft segments of thethermoplastic elastomer because the carbon chain in the repeating unitis rigid due to their chemical structures.

After intensive investigations in view of these circumstances, theinventors have discovered new polyalkylene ether glycol copolymers,preferably having a number-average molecular weight of 200 to 10,000,and having hydroxyl groups at both ends of the molecule in which therecurring structural units of the copolymers are units of the followingformulae (I) and (II), preferably copolymerized in a molar ratio (I/II)in the range of from 1/99 to 99/1: ##STR2##

The polyalkylene ether glycol copolymers of the present invention have2-methylpropylene ether groups (I) and tetramethylene ether groups (II)as repeating units and they have primary hydroxyl groups at both ends.The molar ratio of the units (I) to units (II) is preferably 5/95 to95/5 and the copolymer preferably has a number-average molecular weightof 500 to 6,000. The copolymer of the present invention is quiteflexible due to its chemical structure. The copolymer scarcelycrystallizes even when it has a high molecular weight. The copolymerexhibits sufficient elasticity and elastic recovery effects. Thepolyalkylene ether glycol copolymer, according to the invention, iseasily reactive with carboxyl and isocyanato groups. Thus, it issuitable for use as the soft segments in the production of elastomers ofpolyesters, polyamides, polyurethanes and the like.

The new polyalkylene ether glycol copolymers of the present inventioncan be obtained easily by ring-opening copolymerization of3-methyloxetane with tetrahydrofuran, in the presence of an acidcatalyst. The molar ratio of 3-methyloxetane to tetrahydrofuran beingreacted is not particularly limited. However, the preferred molar ratioof 3-methyloxetane/tetrahydrofuran is 1/99 to 99/1, particularly99-10/1-90. During the reaction to form the copolymer, 3-methyloxetaneand tetrahydrofuran should be present in a3-methyloxetane/tetrahydrofuran molar ratio of higher than 1, since theformer has a reactivity far higher than that of the latter. If the molarratio is less than 1, 3-methyloxetane is consumed rapidly and,consequently, some tetrahydrofuran homopolymer is formed. In someapplications, a polyalkylene ether glycol mixture will suffice andseparation of the homopolymer is unnecessary. Further, a highly randomcopolymer can be obtained by successive addition polymerization of3-methyloxetane. In addition, a block copolymer can be obtained easilyby effecting the polymerization of tetrahydrofuran to a partial extentand then adding 3-methyloxetane to the reaction system to continue thepolymerization. 3-Methyloxetane and tetrahydrofuran can be handledeasily, since they are in liquid form at ambient temperature. Thering-opening copolymerization reaction of them proceeds easily in thepresence of an acid catalyst.

3-Methyloxetane is obtained by, for example, reacting2-methyl-1,3-propanediol with acetyl chloride to obtain3-chloro-2-methylpropyl acetate and then effecting ring closure of theproduct by alkali fusion. As the acid catalysts used in the ring-openingcopolymerization, there can be mentioned hydroacids, such as perchloricacid/fuming sulfuric acid, perchloric/acid/acetic anhydride orfluorosulfonic acid. Although other known catalysts generally used forthe ring-opening polymerization of oxetane, such as borontrifluoride/diethyl ether complex, trialkylaluminum, phosphoruspentafluoride, antimony pentafluoride and various Lewis acids, can beused as the copolymerization catalysts, the above-mentioned hydroacidcatalysts are particularly preferred because hydroxyl groups can beintroduced at both ends of the copolymers by a suitable treatment, suchas saponification in the latter case.

The polyalkylene ether glycol copolymers of the present invention can beused not only as the soft segments of elastomers of polyesters,polyamides, polyurethanes, or the like, but also as lubricants orstarting materials therefor, starting materials for preparing cosmeticsand medicines, starting materials or additives for water-based paints,paper coatings, adhesives, cellophanes, coating inks, abrasives andsurfactants and as starting materials for resins such as alkyd resins.

The following examples will further illustrate the present inventon,which by no means limit the invention. In the examples, parts are givenby weight and the products were identified by the following methods:

(1) Nuclear magnetic resonance spectrum:

A nuclear magnetic resonance device JNM-C-60HL (a product of NihonDenshi Co.) was used for the measurement.

(2) Infrared absorption spectrum:

A grating infrared spectrophotometer IRA-2 (a product of Nihon BunkoCo.) was used for the measurement.

(3) Hydroxyl value:

Hydroxyl value was determined according to JIS K 1557.

( 4) Molecular weight distribution:

The molecular weight distribution was determined at 40° C. at a flowrate of 1.0 ml/min using a high performance liquid chromatographicdevice TRI ROTAR SR (a product of Nihon Bunko Co.), Shodex GPC A-80 M (aproduct of Showa Denko Co.) as the column, differential refractometerShodex RI SE-31 as the detector and tetrahydrofuran as the mobile phase.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an infrared absorption spectrum of the polyether copolymerobtained in Example 1.

FIG. 2 is the nuclear magnetic resonance spectrum thereof.

EXAMPLE 1

100 parts of 2-methyl-1,3-propanediol were mixed with 101 parts ofacetyl chloride. The mixture was heated to 100° C. for 8 h to obtain 151parts (yield: 90%) of 3-chloro-2-methylpropyl acetate. 100 parts of thisacetate were treated with a solution of potassium hydroxide/sodiumhydroxide to obtain 31 parts (yield: 58%) of the ring-closure product,namely, 3-methyloxetane. The 3-methyloxetane thus obtained andtetrahydrofuran were refluxed separately in the presence of metallicsodium for 2 to 3 hours, rectified and subjected to the copolymerizationimmediately thereafter. In the reaction, 79 parts of 3-methyloxetane and21 parts of tetrahydrofuran were charged in a nitrogen-purged, dryreactor. The reactor was cooled externally with a dry ice/methanolfreezing mixture to maintain the internal temperature at -60° C. whilethe contents of the reactor were stirred. Then, 1.53 parts of aceticanhydride were added thereto while the temperature was maintained at-60° C. and 2.35 parts of 70% perchloric acid were slowly added dropwisethereto. The temperature of the reaction mixture was elevated to roomtemperature under stirring for about 5 h and the reaction was continuedat room temperature for an additional 100 h. Thereafter about 300 partsof distilled water was added thereto to terminate the reaction. Thetemperature was elevated to remove unreacted monomers. The mixture waskept at a temperature of about 90° C. under stirring for 2 h. Themixture was left to stand, an aqueous layer thus formed was removed andabout 200 parts of 0.5 N potassium hydroxide/ethanol solution was addedthereto. The mixture was refluxed under stirring for 2 h to saponify theend groups. After completion of the saponification, ethanol wasdistilled off. Benzene was added thereto to form a benzene solution. Aninorganic salt formed by the saponification and excess solid potassiumhydroxide precipitated were filtered off. The filtrate was treated withactive china clay. The product was decolored with active carbon, ifnecessary. The resulting liquid was exactly neutral. Benzene wasexpelled from the liquid completely under reduced pressure to obtain 69parts by weight of the intended polyether copolymer of the presentinvention. The polymerization conversion was 69%.

The thus-obtained polyether copolymer was a colorless, transparent,viscous liquid. The infrared absorption and nuclear magnetic resonancespectra of the product are shown in FIGS. 1 and 2, respectively. In theinfrared absorption spectrum, the characteristic absorption due to thetetramethylene ether group is recognized at 1200 cm⁻¹. From the infraredabsorption and nuclear magnetic resonance spectra, it was revealed thatthe product was a polyether copolymer comprising 91.3 molar % of2-methylpropylene ether group and 8.7 molar % of tetramethylene ethergroup. The average molecular weight calculated from the hydroxyl valuewas 1527.

The molecular weight distribution curve obtained according to the highperformance liquid chromatography comprised a completely symmetricalpeak. Mw/Mn (calculated as polystyrene) was 2.20 (Mw beingweight-average molecular weight and Mn being number-average molecularweight).

EXAMPLE 2

48.6 parts of 3-methyloxetane obtained in the same manner as describedin Example 1, 51.4 parts of tetrahydrofuran purified by dehydrationdistillation and 1.5 parts of acetic anhydride were charged in anitrogen-purged, desiccated reactor. The reactor was cooled externallywith a dry ice/methanol freezing mixture to control the internaltemperature to -60° C. while the contents of the reactor were stirred.Then, 2.3 parts of 70% perchloric acid were added dropwise and slowlythereto. After completion of the addition, the temperature of thereaction mixture was elevated to 40° C. in about 5 h. The stirring wascontinued at that temperature for an additional 20 h. The termination ofthe reaction and purification were effected in the same manner asdescribed in Example 1 to obtain 56 parts of a colorless, transparent,viscous liquid. The polymerization rate was 56%.

From the nuclear magnetic resonance and infrared absorption spectra, itwas revealed that the resulting polyether copolymer contained 78.3 molar% of 2-methylpropylene ether group and 21.7 molar % of tetramethyleneether group. The average molecular weight calculated from the hydroxylvalue was 1264. Mw/Mn determined from the high performance liquidchromatograph was 1.80 (calculated as polystyrene).

EXAMPLE 3

19.1 parts of 3-methyloxetane obtained in the same manner as in Example1 and 80.9 parts of tetrahydrofuran purified by dehydration distillationwere charged in a nitrogen-purged reactor. The reactor was cooledexternally with a dry ice/methanol freezing mixture to control theinternal temperature to -60° C. while the contents of the reactor werestirred. 11.1 parts of fluorosulfonic acid were added dropwise andslowly thereto so as to maintain the internal temperature at -60° C.After completion of the addition, the temperature of the reactionmixture was elevated to 0° C. in about 4 h. The stirring was continuedat that temperature for 10 h. 300 parts of distilled water were added tothe reaction mixture. The mixture was stirred at a temperature of atleast 90° C. for 2 h and then left to stand. A lower aqueous layer thusformed was removed and 300 parts of distilled water were added thereto.This operation was repeated to saponify the end groups of the copolymerinto hydroxyl groups. 300 parts of benzene were added to the separatedreaction product layer and the mixture was stirred to obtain ahomogeneous solution. 2 parts of calcium hydroxide were added to thesolution. After thorough stirring, the acid remaining in the reactionproduct was neutralized. Water contained in the benzene solution wasremoved by azeotropic distillation with benzene. A small amount ofbenzene was added thereto and an inorganic solid suspended in thesolution was filtered off. Benzene was distilled off from the filtrateto obtain 46 parts of a copolymer in the form of a colorless,transparent, viscous liquid. The polymerization conversion was 46%.

From the infrared absorption and nuclear magnetic resonance spectra, itwas revealed that the resulting polyether copolymer comprised 35.8 molar% of 2-methylpropylene ether group and 64.2 molar % of tetramethyleneether group.

The average molecular weight calculated from the hydroxyl value was1825. Mw/Mn determined from the high performance liquid chromatographwas 2.10 (calculated as polystyrene).

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. Polyalkylene etherglycol copolymer having a number-average molecular weight of 500 to10,000 and having hydroxyl groups at both ends of the molecule, saidcopolymer consisting essentially of recurring structural units of thefollowing formulae (I) and (II) in a molar ratio of from 1/99 to 99/1:##STR3##
 2. Polyalkylene ether glycol copolymer according to claim 1wherein the molar ratio of units (I) to units (II) is 5/95 to 95/5 andthe number-average molecular weight of said copolymer is 500 to 6,000.3. Polyalkylene ether glycol copolymer as claimed in claim 1 in whichthe molar ratio of (I)/(II) is 99-10/1-90.
 4. A polyalkylene etherglycol copolymer as claimed in claim 1, wherein said copolymer isprepared by a process which comprises subjecting a mixture of3-methyloxethane and tetrahydrofuran, wherein the3-methyloxetane/tetrahydrofuran molar ratio is higher than 1, toring-opening polymerization in the presence of a catalytically effectiveamount of a hydroacid catalyst under conditions effective to obtain acopolymerized product, then saponifying said copolymerized product toform said copolymer, and then recovering said copolymer.
 5. Apolyalkylene ether glycol copolymer having a number-average molecularweight in the range of 500 to 6,000 and having hydroxyl groups at bothends of the molecule, said copolymer consisting of recurring structuralunits of the following formula (I) and (II) in a molar ratio (I)/(II) of99-10/1-90: ##STR4## said copolymer being prepared by a processconsisting essentially of the steps of:(1) forming a mixture of3-methyloxetane and tetrahydrofuran having a3-methyloxetane/tetrahydrofuran molar ratio higher than 1; (2) thencooling said mixture, adding a catalytically effective amount of ahydroacid catalyst to said mixture to thereby effect a ring-openingpolymerization reaction of 3-methyloxetane with tetrahydrofuran, thenwarming said mixture; (3) then adding water to said mixture to terminatethe reaction and obtain a copolymerized product; (4) then saponifyingthe end groups of said product to form said copolymerized copolymer; (5)then recovering said copolymer.
 6. A polyalkylene ether glycol copolymeras claimed in claim 5, wherein in said step (2), said mixture is firstcooled to about -60° C., then said hydroacid catalyst is added, saidhydroacid catalyst consisting of acetic anhydride and perchloric acid,then said mixture is warmed to at least 0° C. to conduct said reaction.7. A polyalkylene ether glycol copolymer as claimed in claim 5, whereinsaid hydroacid catalyst is selected from the group consisting ofperchloric acid/fuming sulfuric acid, perchloric acid/acetic anhydride,and fluorosulfonic acid.
 8. A polyalkylene ether glycol copolymer asclaimed in claim 5, wherein said copolymer has the infrared absorptionspectrum given in FIG. 1 of the drawings referred to in the foregoingspecification.
 9. A polyalkylene ether glycol copolymer as claimed inclaim 5, wherein said copolymer has the nuclear magnetic resonancespectrum given in FIG. 2 of the drawings referred to in the foregoingspecification.
 10. A polyalkylene ether glycol copolymer as claimed inclaim 5, wherein said copolymer has a ratio M_(w) /M_(n), calculated aspolystyrene, in the range of 1.80 to 2.20, and the average molecularweight of said copolymer calculated from the hydroxyl value thereof isin the range of 1,264 to 1,825.